Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$52.28	5.690%	$55.2547	$55.25	$55.25	$55.30
Purchase #2	$19.43	7.388%	$20.8655	$20.87	$20.85	$20.90
Purchase #3	$17.65	4.273%	$18.4042	$18.40	$18.40	$18.40
Purchase #4	$220.81	6.547%	$235.2664	$235.27	$235.25	$235.30
Purchase #5	$222.31	8.169%	$240.4705	$240.47	$240.45	$240.50
Purchase #6	$184.75	3.632%	$191.4601	$191.46	$191.45	$191.50
Purchase #7	$111.72	9.709%	$122.5669	$122.57	$122.55	$122.60
7 purchase totals =	$828.95		$884.2883	$884.29	$884.20	$884.50